He was born in Gunma Prefecture and graduated from Gunma Prefectural Maebashi High School and the department of humanities at Tokyo University of Education. He started a master's degree at the same university but did not complete it. After serving as a teacher in the faculty of education of Utsunomiya University, he has worked regularly since 1999 at the Nanjing MassacreResearch Center of Nanjing Normal University as a visiting professor and, since 2000, in the same capacity in the department of history at Nankai University. He is a researcher on the Nanjing Massacre that occurred in the early stages of the Second Sino-Japanese War. Although he acknowledges that the death toll for the massacre of over 300,000 used by Nanjing Massacre Memorial Hall is a baseless overestimate, he takes the position that “between more than 100,000 and about 200,000” were massacred not only in the city but also in the surrounding areas and six neighbouring counties though “there is a possibility this number will continue to increase based on future discoveries and disclosures of data and the future course of research.” Originally the modern economic history of China was his area of expertise, but in the middle of the 1980s he began research into the Nanjing Massacre and upon involving himself in the debate on how Japanese perceive their history his research on military history became dominant. Currently he is participating as a Japanese representative at an international textbook conference that is sponsored by a Korean-based foundation of northeast Asian history and the Peace Boat.
Apology over misused photograph
On the first page of chapter 3 of his 1997 book Nankin Jiken, Kasahara published a photograph with the caption “Chinese women from the Jiangnan region who are being abducted by the Japanese army” from a 1938 copy of the Riguan Baohang Shilu, a publication of the Politburo of the Military Committee of the ROC, that he had seen at the Hoover Institution’s East Asia Collection at Stanford University. However, it was pointed out by Ikuhiko Hata that the photograph was originally published in the Asahi Graph on 10 November 1937 and actually said it was “a group of girls of the ‘Rising Sun’ village who are returning to the village from farm work with the assistance of our troops". Kasahara personally apologized for not noticing that this picture taken by an Asahi Shimbun photographer had been misused by the Riguan Baohang Shilu. Accepting this, his publisher Iwanami Shoten temporarily ceased putting the book in exhibits and published on the same page a written apology entitled “to all readers.” With Kasahara’s consent they swapped it with a photo from the book Morase Moriyasu Shashinshū: Watashi no Jūgun Chūgoku Sensen of an old woman who says that she was raped by Japanese soldiers, and they agreed to replacements of the first edition.
